Q: Why do I need a prescription?
A: When you are given a prescription for a medication for your pet, it means that your veterinarian has made a decision that the medication is recommended or necessary to treat your pet's health problem. Many prescription drugs are only effective for specific problems, and may actually be harmful to your pet if used without that critical veterinary examination and diagnosis. Having these drugs available as prescription-only medications ensures that they are used appropriately.
Let's take heartworm preventives as an example. Heartworm preventives are labeled as "prescription-only" because it's critical that your veterinarian makes sure the medication is the right one based on your pet's health status. The preventives target the infective larvae as they are migrating through the tissue prior to reaching the bloodstream and developing to adult heartworms. If your dog (or cat) has heartworms, giving a preventive medication will not effectively treat the disease because the preventives don't readily kill adult heartworms. In some cases, administering preventives to heartworm positive dogs can cause a rapid kill of circulating microfilariae, leading to a life-threatening anaphylactic reaction.
There are drugs, called "over the counter" (OTC) drugs, that don't require prescriptions. Drugs can be bought OTC when the Food and Drug Administration (FDA) determines that the directions for the drug's use aren't overly complicated and are adequate for the public to follow. In some cases, such as the common headache medications for people, the OTC version is just a weaker strength than the prescription form. However, in many cases, a medication is only available with a prescription for the reasons we mention above.
Q: What's the difference between the brand name, trade name and generic name of a medication?
A: Brand names and trade names are also called proprietary names, and are just what they sound like – they are the trademarked names you recognize on the shelves and see in advertisements. The generic name, on the other hand, is the nonproprietary name of the drug and is the same for all versions (brand-name and otherwise) of that drug. For example, take ibuprofen: there are several brand names for the drug, including Motrin® and Advil®, but the generic name of the drug is ibuprofen. If you were to buy the brand/trade name of the drug (for yourself, not your pet), you'd purchase Motrin® or Advil®, but if you were to buy the generic version, it would just be labeled "ibuprofen."
Q: Is there a difference between the brand name version and the generic version of a medication?
A: For the most part, no. The United States Pharmacopeia (USP) sets the standards for the quality, purity, strength and consistency of all prescription and OTC medications in the U.S. – the goal is to make sure that the product you purchase meets these standards. If you look closely at the drug labels, you'll see "USP" printed after the drug name in the ingredients list – and sometimes it's printed clearly on the front label of the bottle/box. Based on USP standards, for example, generic ibuprofen is the same drug as the brand name-versions of ibuprofen (of the same strength) as far as the quality, purity, and consistency are concerned.
However, we have heard some anecdotal and unconfirmed reports of pets that had been receiving a brand name medication, but did not do as well when given a generic version of the same medication. Although all USP versions of a drug meet the purity standards for that drug, all of the ingredients and the processes involved in making the trade name versions are often protected by patent or other intellectual property laws, and there may be differences in the minor ingredients that could produce slightly different results between the versions, while still providing the main drug that meets USP standards. Think of it as following a recipe – even if you have the same ingredients and follow the instructions, the end result might vary a little bit. This is not a common problem with medications, and is often resolved by switching back to the effective version of the medication.